Alright, after a long night, the morning after, and a lot of copy-and-pasting, here's what I've found.
Today Target is working better. No the 5% is not gone, it was just not working last night. Not for EBay GCs, not for Disney GCs.
* Cardpool... bought 3 groups of around $242 ($256.50 value). Each time got the codes w/in minutes. 6% off.
* Target... bought 3 $100 EBay's last night. Could not get more of anything. Orders kept cancelling an hour later. Could not even get Disney (cart kept emptying glitch), which was good, cuz by waiting I got EBay's again this morning. Today I got 12 $50 ones (in 4 orders, ack!). I didn't try the $100's. Each purchase of $300 costs around $256.50.. (which is why I buy Cardpool in that increment). 10% off (sale) then 5% off (redcard)
* Ordering on EBay. Oh my. Could not apply more than 4 Redemption codes to one order. This was annoying cuz I got the $50 ones. Ok fine. So ordered them in $200 increments. 2nd holdup... could not keep using the same Paypal account beyond the 2nd transaction. It seems there is a limit on how many consecutive redemption credits you can use attributed to one Paypal account. But we switched to our other one and were able to get the orders thru. So now I've got an order of $300 (yesterday) and 3 orders of $200 (today). When these arrive, it should be $900 worth of Target GC. (This is around a 2% loss due to shipping but that's ok)
* That $900 Target GC will buy $950 worth of Disney GC (putting in $2.50 of my own because $950 Disney GC costs $902.50).
So net result, I put in
$724.04 to Cardpool
$16.91 in Ebay shipping
$2.50 at the end
Total invested: $743.45
Total begotten: $950.00
$206.55 saved... 22%. This beat my previous running savings of about 14%, and even beat my previous best set which was Black Friday-Target-Disney-DVA which was 16.4%. Nice.

It could have been better if Target GCs were cheaper on Ebay or if I could have put more than 2 GCs on an Ebay order (to minimize the shipping loss). If I needed to pay more on our room I'd put these funds into my DVA for another 2%, but this is just for dining so I'll hold the Disney GCs.
I could use more still, but I'm going to stop there and not press my luck since I'm concerned about that Paypal Redemption code limit. I'd hate to get stuck w money locked up in Ebay codes that I won't use any time soon.
Hope that helps!
Oh and a big thank you to everyone who helped put their heads together on this!